Suppose x is any positive number. Circle 1 has a center at (-2, 7) and a radius of 8x. Circle 2 has a center at (-3, 0) and a radius of 5x. Why is circle 1 similar to circle 2?

(x-center) ^2 + (y-center) ^2=r^2

C1: (x - (-2)) ^2 + (y-7) ^2 = (8x) ^2

C1: (x+2) ^2 + (y-7) ^2=64x^2

C2: (x - (-3)) ^2 + (y-0) ^2 = (5x) ^2

C2: (x+3) ^2+y^2=25x^2

C1 is similar to C2 in that they both are centered left of the y-axis, and both have a radius including an x^2 value which is not usual.